The present study aims to analyze climate change and trend of extreme temperature events occurred over the Republic of Korea. The observation data used are daily average, maximum, and minimum temperature from 6 weather stations for the period of 1912-2020. Seven extreme indices regarding frequency and extreme value of temperature are calculated in seasonal and annual time range. In addition, hot extremes and their changes by four physical terms that include information on the annual mean temperature, the amplitude of the annual cycle, the diurnal temperature range and the local temperature anomaly on the day of the extreme are analyzed. The climatology for the analysis is updated to the new normal year of 1991-2020. Consistent with the previous findings, statistically significant change was detected in the indices of annual lowest daily minimum temperature, annual extreme temperature range, frequency of daily minimum temperature below -12℃ and 10%ile(TN10p) during winter. Due to the gradual decrease of the occurrence days regarding the extreme minimum temperature during winter, the frequency calculated by the relative threshold in extreme high temperature during summer prevail since 1990s. Indices related with extreme high temperature had larger low-frequency variability than significant climate change during the analysis period. However, the assessment of hot extremes according to the terms describing mean, variability and tails during the new normal year of 1991-2020, significant increasing trend was detected not only in the annual mean and the amplitude of the seasonal cycle, but also in the daily hot extreme anomaly.

This paper has presented not only the spatial coverage change of climate extreme events in summer and winter seasons during the period of 2000-2017, but also their future projections in 2021-2100, South Korea through analysis of a Combined Climate Extreme Index (CCEI). The CCEI quantifies the spatial coverage of climate extreme events based on a set of five indicators. MK (Modified Korean)-PRISM (Parameter-elevation Regression on Independent Slopes Model)v1.2 (1×1km) and RCP scenario data (1×1km) were applied to CCEI. Results indicated that in average, 21.7% of the areas in the summer and 23.6% in the winter experienced climate extremes from 2000 to 2017 regardless of types of climate extreme events in South Korea. The summer of 2003 and 2009 was relatively cool and humid, while the summer of 2014 and 2015 was cool and dry and the summer of 2016 was warm and dry. The extreme events with much above normal maximum and minimum temperature during the study period were detected but not much below normal maximum and minimum temperature after 2015. For RCP2.6 and RCP8.5 scenarios, there were statistically significant trends with spatial coverage expansion of climate extreme events in the future. It might be concluded that climate extreme events in the summer and winter seasons were affected simultaneously by two or more indicators than a single indicator in South Korea.

In this study, we analyzed the characteristics of climate variability in summer rainfall during Changma over three sub-sector regions (Middle, Southern, Jeju) in South Korea for the new climatological period of 1991- 2020 using observation data from 60 ASOS stations. There was a significant interannual variability in rainfall, wet days, and rainfall intensity but the long-term trend of rainfall was not significant over the three sectors in South Korea. Comparing the new climatology (P2: 1991-2020) with the old one (P1: 1981-2010), it was found that the precipitation during Changma in new climatology (P2) was enhanced in Middle sector but reduced in Southern and Jeju sectors. In P2, wet days increased only a few stations in the Middle sector but the rainfall intensity was strengthened over the 50% stations including Middle sector, south and west coast of the Southern sector. Wet days above 25, 50, 75, 95%ile rainfall during Changma in Southern and Jeju sectors all decreased in P2. Climatological change from P1 to P2 showed a large variability not only in temporal frame but also in the spatial distribution in South Korea.

An application of an integrated climate extreme index (CEI) is presented, that quantifies observed climate change of South Korea by various five indicators. Based on an annual basis surface observation station data, climate extreme indicators that measure the fraction of the stations in South Korea are analyzed. Results for the annual CEI indicate that the area experiencing much above-normal maximum and minimum temperatures in recent years has been increased. The extremes in much greater-than-normal number of days with or without precipitation has a large interannual variability similar with much above and below normal standardized precipitation index. Results from above-normal proportion of heavy daily precipitation show a more pronounced increasing feature from 1990’s to the early 2010’s. Five indicators in CEI had distinct contrasting features which indicates that CEI can be a useful tool in providing the information on the percentage of the climate in South Korea that experienced various kinds of extreme conditions during any given year or period.

This study had two main objectives. We first investigated which weather phenomena people were most concerned about in the context of climate change or global warming. Then, we conducted content analysis to find which words were more commonly used with climate change or global warming. For this, we collected web data from Twitter, Naver, and Daum from April to October 2019 in the Republic of Korea. The results suggested that people were more concerned about air quality, followed by typhoons and heat waves. Because this study only considered one warm period in the year of 2019, winter-related weather phenomena such as cold wave and snowfall were not well captured. From Twitter, we were able to find wider range of terminologies and thoughts/opinions than Naver and Daum. Also, more life-relevant weather events such as typhoons and heat waves in Twitter were commonly mentioned compared to Naver and Daum. On the other hand, the comments from Naver and Daum showed relatively narrower and limited terms and thoughts/ opinions. Especially, most of the comments were influenced by headlines of articles. We found many comments about air quality and energy/economic policy. We hope this paper could provide background information about how to promote the climate change education and public awareness and how to efficiently interact with general audiences.

Cell based grid data of future temperature and precipitation produced with four RCP scenarios were converted into polygon based data for administrative districts using three simple vectorizing methods; (1) KMA Dong-Nae forecast point based, (2) areal ratio based and (3) central point based methods. The results were compared the existed KMA areal weight based methods to identify which methods were more efficient than others. Simple statistical methods such descriptive statistics, correlation coefficient, and Bland & Altman plots (B&A) were used to compare agreements between them. When central point and areal ratio based methods were applied to administrative districts of Eup-Myeon-Dong or some Gus, NULLs were found because their sizes are smaller than the cell of 1x1 km. Therefore, KMA Dong-Nae forecast point based methods were better when sizes of administrative districts are smaller than the cell size. For Do and Metropolitan cities, there were no greater differences among methods except for the KMA Dong- Nae forecast points. The greater the areas of administrative districts the more distortions from the KMA Dong-Nae forecast points because only KMA Dong-Nae forecast one point were used for the calculation. In conclusion, the KMA Dong-Nae forecast point based method was appropriate when sizes of administrative districts are smaller than the grid cell. For the greater areal sizes such as Do and Metropolitan cities, areal ratio and central point based methods were better.

In this study, we analyzed the characteristics of summer extreme rainfall over South Korea and their relationships with the synoptic and large-scale circulation anomalies during 1979-2014. Heavy rainfall (R90p) is related with the strong convection surrounded by dry zone over Korean peninsula and the moist air delivered from the convection area over Bay of Bengal-South China Sea-Philippine Sea. The upper-level anticyclonic flow with the low-level dipole of anticyclonic circulation in the Southeast and cyclonic circulation to the northwest of Korean peninsula are the main characteristics when the extreme rainfall occurs. The barotropic Rossby wave developed over the Korean peninsula transfers its energy farther downstream to the western coast of North America. It is also found that the dominant lowfrequency oscillation over the tropics (intraseasonal oscillation) play an important background role for the enhancement of extreme rainfall over South Korea.

In this study, we analyzed the characteristics of summer rainfall over South Korea during recent five(2009-2013) years using observation data. There was a significant contrast in interannual variability between July and August rainfall since 1998. Large increase of rainfall in July (2009 and 2011) and August (2010 and 2012) were found to be consistent over all 60 stations in South Korea. Enhanced precipitation over western tropical Paciÿc and anticyclonic anomaly to the east of Korean peninsula were the common features when there was rainfall increase both in July and August. Intraseasonal summer rainfall over South Korea evolves in time lag with intraseasonal Indian and Western North Pacific monsoon indices. The meridional tripole structure of intraseasonal convection from the Western North Pacific to East Asia and the baroclinic structure of intraseasonal circulation anomalies centered over Korean peninsula provided a favorable condition for the extreme rainfall(90 percentile) events to occur.

In this study, we analyzed the intraseasonal variability and change of winter temperature over South Korea using long-term observations. The lowest temperature in the wintertime, using daily mean, maximum, and minimum temperature data occurred on January 7th in the period of 2003~2012, while on January 22~25th in the past 30 years(1973~1982, 1983~1992, 1993~2002). Representative seven stations in South Korea also showed consistent result. The strengthening of Siberian High and weakening of Aleutian Low in recent 10 years are found to be closely related with the recent intraseasonal temperature change over South Korea. The baroclinic structure of upper-level low and lower-level high system near Korean peninsula provided good condition for vertical cold-air advection, which resulted in minimum temperature on late January in 1973~1982 and early January in 2003~2012 with strengthened low-level northerly flow.

Intraseasonal variability of the tropical convection over the Indian/western Pacific is studied using the Geostationary Meteorological Satellite high cloud amount. This study is directed to find the tropical-extratropical interaction in the frequency range of intraseasonal and interannual variabilities of the summer monsoon occured over the domain of 90E-171W and 49S-50N. Especially, in order to investigate the intraseasonal interaction of East Asia summer monsoon associated with the tropical convections in the high cloud amounts, the spatial and time structure of the intraseasonal oscillation for the movement and the evolution of the large-scale convections are studied. To describe the spatial and the time evolution, the extended empirical orthogonal function analysis is applied. The first mode may be considered to a normal structure, indicating that the strong convection band over 90E-120E is extended to eastward, but this mode was detected as a variable mode near Korea and Japan. The second, third and fourth modes were amplified with the intraseasonal variability during summer monsoon. It is found that the dominant intraseasonal mode of the tropical convection consists of the spatial changes over a broad period range centered around 40∼50days.